Atmospheric composition change: Ecosystems–Atmosphere interactions

Ecosystems and the atmosphere: This review describes the state of understanding the processes involved in\r\nthe exchange of trace gases and aerosols between the earth’s surface and the atmosphere. The gases\r\ncovered include NO, NO2, HONO, HNO3, NH3, SO2, DMS, Biogenic VOC, O3, CH4, N2O and particles in the size\r\nrange 1 nm–10 mmincluding organic and inorganic chemical species. The main focus of the reviewis on the\r\nexchange between terrestrial ecosystems, both managed and natural and the atmosphere, although some\r\nnew developments in ocean–atmosphere exchange are included. The material presented is biased towards\r\nthe last decade, but includes earlier work, where more recent developments are limited or absent.\r\nNew methodologies and instrumentation have enabled, if not driven technical advances in measurement.\r\nThese developments have advanced the process understanding and upscaling of fluxes, especially\r\nfor particles, VOC and NH3. Examples of these applications include mass spectrometric methods, such as\r\nAerosol Mass Spectrometry (AMS) adapted for field measurement of atmosphere–surface fluxes using\r\nmicrometeorological methods for chemically resolved aerosols. Also briefly described are some advances\r\nin theory and techniques in micrometeorology.\r\nFor some of the compounds there have been paradigm shifts in approach and application of both techniques\r\nand assessment. These include flux measurements over marine surfaces and urban areas using\r\nmicrometeorological methods and the up-scaling of flux measurements using aircraft and satellite remote\r\nsensing. The application of a flux-based approach in assessment of O3 effects on vegetation at regional scales\r\nis an important policy linked development secured through improved quantification of fluxes. The coupling\r\nof monitoring, modelling and intensive flux measurement at a continental scale within the NitroEurope\r\nnetwork represents a quantum development in the application of research teams to address the underpinning\r\nscience of reactive nitrogen in the cycling between ecosystems and the atmosphere in Europe.\r\nSome important developments of the science have been applied to assist in addressing policy questions,\r\nwhich have been the main driver of the research agenda, while other developments in understanding have\r\nnot been applied to their wider field especially in chemistry-transport models through deficiencies in\r\nobtaining appropriate data to enable application or inertia within the modelling community. The paper\r\nidentifies applications, gaps and research questions that have remained intractable at least since 2000\r\nwithin the specialized sections of the paper, and where possible these have been focussed on research\r\nquestions for the coming decade.